Familial hypertrophic cardiomyopathy (FHC), an inherited disease with a high incidence of premature death due to cardiac failure, has its genetic loci in the contractile proteins in the heart. Thus, FHC may be a disease of the sarcomere, muscle's most basic contractile unit. In the sarcomere, myosin, a molecular motor, interacts with actin to generate the power of the heart. This Program Project (3 projects and 3 cores) focuses on mutations to myosin and the actin regulatory proteins, troponinT, and tropomyosin. Using state-of-the-art techniques, we will characterize FHC from the mechanics of the whole heart down the molecular mechanics of a single contractile protein, to assess how structural alterations to these proteins affect the mechanical properties of the sarcomere, the muscle fiber, and the whole heart. Project #1 will study the mechanical properties of the whole heart and papillary muscles obtained from transgenic mice with mutations in either myosin, troponinT, or alpha- tropomyosin. Project #2 will genetically engineer FHC mutations into myosin using an in vitro protein expression system. Project #2 will biochemically characterize these proteins, while project #3 will use the laser optical trap to assess the force and motion generating capacity of these mutants at the single molecule level. All projects use the Analytical and Modeling Core (Unit B) for expertise in data collection, analysis, and modeling. In addition, the Mouse Production and Ventricular Function Core (Unit C) will generate mice with FHC mutant hearts that will be studied at all anatomical levels by the various projects. In addition, this Core will also characterize the in vivo ventricular performance of the hearts within the transgenic mice. The long-term goals are: 1) to utilize FHC-related point mutations as a means of identifying key structural domains within the mutant sarcomeric proteins and to determine how these domains relate to the protein's molecular function; 2) to understand how point mutations in contractile proteins compromise sarcomere function, and how these mutations, in turn, may trigger cardiac hypertrophy.